Photon tunneling effects give rise to surface waves, amplifying radiative heat transfer in the near-field regime. Recent research has highlighted that the introduction of nanopores into materials creates additional pathways for heat transfer, leading to a substantial enhancement of near-field radiative heat transfer (NFRHT). Being a direct bandgap semiconductor, GaN has high thermal conductivity and stable resistance at high temperatures, and holds significant potential for applications in optoelectronic devices. Indeed, study of NFRHT between nanoporous GaN films is currently lacking, hence the physical mechanism for adding nanopores to GaN films remains to be discussed in the field of NFRHT. In this work, we delve into the NFRHT of GaN nanoporous films in terms of gap distance, GaN film thickness and the vacuum filling ratio. The results demonstrate a 27.2% increase in heat flux for a 10 nm gap when the nanoporous filling ratio is 0.5. Moreover, the spectral heat flux exhibits redshift with increase in the vacuum filling ratio. To be more precise, the peak of spectral heat flux moves from ω = 1.31×10¹⁴ rad·s^-1 to ω = 1.23×10¹⁴ rad·s^-1 when the vacuum filling ratio changes from f = 0.1 to f = 0.5; this can be attributed to the excitation of surface phonon polaritons. The introduction of graphene into these configurations can highly enhance the NFRHT, and the spectral heat flux exhibits a blueshift with increase in the vacuum filling ratio, which can be explained by the excitation of surface plasmon polaritons. These findings offer theoretical insights that can guide the extensive utilization of porous structures in thermal control, management and thermal modulation.

GeTe has attracted extensive research interest for thermoelectric applications. In this paper, we first train a neuro-evolution potential (NEP) based on a dataset constructed by ab initio molecular dynamics, with the Gaussian approximation potential (GAP) as a reference. The phonon density of states is then calculated by two machine learning potentials and compared with density functional theory results, with the GAP potential having higher accuracy. Next, the thermal conductivity of a GeTe crystal at 300 K is calculated by the equilibrium molecular dynamics method using both machine learning potentials, and both of them are in good agreement with the experimental results; however, the calculation speed when using the NEP potential is about 500 times faster than when using the GAP potential. Finally, the lattice thermal conductivity in the range of 300 K—600 K is calculated using the NEP potential. The lattice thermal conductivity decreases as the temperature increases due to the phonon anharmonic effect. This study provides a theoretical tool for the study of the thermal conductivity of GeTe.

Zinc oxide (ZnO) shows great potential in electronics, but its large intrinsic thermal conductivity limits its thermoelectric applications. In this work, we explore the significant carrier transport capacity and diameter-dependent thermoelectric characteristics of wurtzite-ZnO<0001> nanowires based on first-principles and molecular dynamics simulations. Under the synergistic effect of band degeneracy and weak phonon—electron scattering, P-type (ZnO)₇₃ nanowires achieve an ultra-high power factor above 1500 μW· cm^-1· K^-2 over a wide temperature range. The lattice thermal conductivity and carrier transport properties of ZnO nanowires exhibit a strong diameter size dependence. When the ZnO nanowire diameter exceeds 12.72 Å, the carrier transport properties increase significantly, while the thermal conductivity shows a slight increase with the diameter size, resulting in a ZT value of up to 6.4 at 700 K for P-type (ZnO)₇₃. For the first time, the size effect is also illustrated by introducing two geometrical configurations of the ZnO nanowires. This work theoretically depicts the size optimization strategy for the thermoelectric conversion of ZnO nanowires.

The combination of different nanostructures can hinder phonons transmission in a wide frequency range and further reduce the thermal conductivity (TC). This will benefit the improvement and application of thermoelectric conversion, insulating materials and thermal barrier coatings, etc. In this work, the effects of nanopillars and Ge nanoparticles (GNPs) on the thermal transport of Si nanowire (SN) are investigated by nonequilibrium molecular dynamics (NEMD) simulation. By analyzing phonons transport behaviors, it is confirmed that the introduction of nanopillars leads to the occurrence of low-frequency phonons resonance, and nanoparticles enhance high-frequency phonons interface scattering and localization. The results show that phonons transport in the whole frequency range can be strongly hindered by the simultaneous introduction of nanopillars and nanoparticles. In addition, the effects of system length, temperature, sizes and numbers of nanoparticles on the TC are investigated. Our work provides useful insights into the effective regulation of the TC of nanomaterials.

Grasping the underlying mechanisms behind the low lattice thermal conductivity of materials is essential for the efficient design and development of high-performance thermoelectric materials and thermal barrier coating materials. In this paper, we present a first-principles calculations of the phonon transport properties of Janus Pb₂PAs and Pb₂SbAs monolayers. Both materials possess low lattice thermal conductivity, at least two orders of magnitude lower than graphene and h-BN. The room temperature thermal conductivity of Pb₂SbAs (0.91 W/mK) is only a quarter of that of Pb₂PAs (3.88 W/mK). We analyze in depth the bonding, lattice dynamics, and phonon mode level information of these materials. Ultimately, it is determined that the synergistic effect of low group velocity due to weak bonding and strong phonon anharmonicity is the fundamental cause of the intrinsic low thermal conductivity in these Janus structures. Relative regular residual analysis further indicates that the four-phonon processes are limited in Pb₂PAs and Pb₂SbAs, and the three-phonon scattering is sufficient to describe their anharmonicity. In this study, the thermal transport properties of Janus Pb₂PAs and Pb₂SbAs monolayers are illuminated based on fundamental physical mechanisms, and the low lattice thermal conductivity endows them with the potential applications in the field of thermal barriers and thermoelectrics.

Controlling mass transportation using intrinsic mechanisms is a challenging topic in nanotechnology. Herein, we employ molecular dynamics simulations to investigate the mass transport inside carbon nanotubes (CNT) with temperature gradients, specifically the effects of adding a static carbon hoop to the outside of a CNT on the transport of a nanomotor inside the CNT. We reveal that the underlying mechanism is the uneven potential energy created by the hoops, i.e., the hoop outside the CNT forms potential energy barriers or wells that affect mass transport inside the CNT. This fundamental control of directional mass transportation may lead to promising routes for nanoscale actuation and energy conversion.

Relative rotation between the emitter and receiver could effectively modulate the near-field radiative heat transfer (NFRHT) in anisotropic media. Due to the strong in-plane anisotropy, natural hyperbolic materials can be used to construct near-field radiative modulators with excellent modulation effects. However, in practical applications, natural hyperbolic materials need to be deposited on the substrate, and the influence of substrate on modulation effect has not been studied yet. In this work, we investigate the influence of substrate effect on near-field radiative modulator based on α-MoO₃. The results show that compared to the situation without a substrate, the presence of both lossless and lossy substrate will reduce the modulation contrast (MC) for different film thicknesses. When the real or imaginary component of the substrate permittivity increases, the mismatch of hyperbolic phonon polaritons (HPPs) weakens, resulting in a reduction in MC. By reducing the real and imaginary components of substrate permittivity, the MC can be significantly improved, reaching 4.64 for ε_s = 3 at t = 10 nm. This work indicates that choosing a substrate with a smaller permittivity helps to achieve a better modulation effect, and provides guidance for the application of natural hyperbolic materials in the near-field radiative modulator.

Thermal illusion aims to create fake thermal signals or hide the thermal target from the background thermal field to mislead infrared observers, and illusion thermotics was proposed to regulate heat flux with artificially structured metamaterials for thermal illusion. Most theoretical and experimental works on illusion thermotics focus on two-dimensional materials, while heat transfer in real three-dimensional (3D) objects remains elusive, so the general 3D illusion thermotics is urgently demanded. In this study, we propose a general method to design 3D thermal illusion metamaterials with varying illusions at different sizes and positions. To validate the generality of the 3D method for thermal illusion metamaterials, we realize thermal functionalities of thermal shifting, splitting, trapping, amplifying and compressing. In addition, we propose a special way to simplify the design method under the condition that the size of illusion target is equal to the size of original heat source. The 3D thermal illusion metamaterial paves a general way for illusion thermotics and triggers the exploration of illusion metamaterials for more functionalities and applications.

The drive for efficient thermal management has intensified with the miniaturization of electronic devices. This study explores the modulation of phonon transport within graphene by introducing silicon nanoparticles influenced by van der Waals forces. Our approach involves the application of non-equilibrium molecular dynamics to assess thermal conductivity while varying the interaction strength, leading to a noteworthy reduction in thermal conductivity. Furthermore, we observe a distinct attenuation in length-dependent behavior within the graphene—nanoparticles system. Our exploration combines wave packet simulations with phonon transmission calculations, aligning with a comprehensive analysis of the phonon transport regime to unveil the underlying physical mechanisms at play. Lastly, we conduct transient molecular dynamics simulations to investigate interfacial thermal conductance between the nanoparticles and the graphene, revealing an enhanced thermal boundary conductance. This research not only contributes to our understanding of phonon transport but also opens a new degree of freedom for utilizing van der Waals nanoparticle-induced resonance, offering promising avenues for the modulation of thermal properties in advanced materials and enhancing their performance in various technological applications.

Through equilibrium and non-equilibrium molecular dynamics simulations, we have demonstrated the inhibitory effect of composition graded interface on thermal transport behavior in lateral heterostructures. Specifically, we investigated the influence of composition gradient length and heterogeneous particles at the silicene/germanene (SIL/GER) heterostructure interface on heat conduction. Our results indicate that composition graded interface at the interface diminishes the thermal conductivity of the heterostructure, with a further reduction observed as the length increases, while the effect of the heterogeneous particles can be considered negligible. To unveil the influence of composition graded interface on thermal transport, we conducted phonon analysis and identified the presence of phonon localization within the interface composition graded region. Through these analyses, we have determined that the decrease in thermal conductivity is correlated with phonon localization within the heterostructure, where a stronger degree of phonon localization signifies poorer thermal conductivity in the material. Our research findings not only contribute to understanding the impact of interface gradient-induced phonon localization on thermal transport but also offer insights into the modulation of thermal conductivity in heterostructures.

Electromagnetic absorbing materials may convert electromagnetic energy into heat energy and dissipate it. However, in a high-power electromagnetic radiation environment, the temperature of the absorbing material rises significantly and even burns. It becomes critical to ensure electromagnetic absorption performance while minimizing temperature rise. Here, we systematically study the coupling mechanism between the electromagnetic field and the temperature field when the absorbing material is irradiated by electromagnetic waves. We find out the influence of the constitutive parameters of the absorbing materials (including uniform and non-uniform) on the temperature distribution. Finally, through a smart design, we achieve better absorption and lower temperature simultaneously. The accuracy of the model is affirmed as simulation results aligned with theoretical analysis. This work provides a new avenue to control the temperature distribution of absorbing materials.

Thermal transistor, the thermal analog of an electronic transistor, is one of the most important thermal devices for microscopic-scale heat manipulating. It is a three-terminal device, and the heat current flowing through two terminals can be largely controlled by the temperature of the third one. Dynamic response plays an important role in the application of electric devices and also thermal devices, which represents the devices' ability to treat fast varying inputs. In this paper, we systematically study two typical dynamic responses of a thermal transistor, i.e., the response to a step-function input (a switching process) and the response to a square-wave input. The role of the length $L$ of the control segment is carefully studied. It is revealed that when $L$ is increased, the performance of the thermal transistor worsens badly. Both the relaxation time for the former process and the cutoff frequency for the latter one follow the power-law dependence on $L$ quite well, which agrees with our analytical expectation. However, the detailed power exponents deviate from the expected values noticeably. This implies the violation of the conventional assumptions that we adopt.

Aerogel nanoporous materials possess high porosity, high specific surface area, and extremely low density due to their unique nanoscale network structure. Moreover, their effective thermal conductivity is very low, making them a new type of lightweight and highly efficient nanoscale super-insulating material. However, prediction of their effective thermal conductivity is challenging due to their uneven pore size distribution. To investigate the internal heat transfer mechanism of aerogel nanoporous materials, this study constructed a cross-aligned and cubic pore model (CACPM) based on the actual pore arrangement of SiO$_{2}$ aerogel. Based on the established CACPM, the effective thermal conductivity expression for the aerogel was derived by simultaneously considering gas-phase heat conduction, solid-phase heat conduction, and radiative heat transfer. The derived expression was then compared with available experimental data and the Wei structure model. The results indicate that, according to the model established in this study for the derived thermal conductivity formula of silica aerogel, for powdery silica aerogel under the conditions of $T=298$K, $a_{2} =0.85$, $D_{1} =90μ $m, $\rho =128{\rm kg/m}^{3}$, within the pressure range of 0-10$^{5}$Pa, the average deviation between the calculated values and experimental values is 10.51%. In the pressure range of 10$^{3}$-10$^{4}$Pa, the deviation between calculated values and experimental values is within 4%. Under these conditions, the model has certain reference value in engineering verification. This study also makes a certain contribution to the research of aerogel thermal conductivity heat transfer models and calculation formulae.

Since the superior mechanical, chemical and physical properties of high-entropy alloys (HEAs) were discovered, they have gradually become new emerging candidates for renewable energy applications. This review presents the novel applications of HEAs in thermoelectric energy conversion. Firstly, the basic concepts and structural properties of HEAs are introduced. Then, we discuss a number of promising thermoelectric materials based on HEAs. Finally, the conclusion and outlook are presented. This article presents an advanced understanding of the thermoelectric properties of HEAs, which provides new opportunities for promoting their applications in renewable energy.